1. Field of the Invention
The present invention relates to a substrate processing apparatus for processing substrates, a substrate processing method, and a storage medium storing a computer program for performing the substrate processing method.
2. Description of Related Art
There has been known a substrate processing apparatus that subjects a substrate, such as a semiconductor wafer (hereinafter referred to simply as “wafer”), to a chemical liquid process (etching process) by immersing the wafer into a chemical liquid (etching liquid) stored in a process tank (see, JP2001-23952A, for example). In such a substrate processing apparatus, a plurality of (e.g., fifty) wafers each having a silicon nitride film formed on a surface thereof are immersed into a boiling chemical liquid (e.g., phosphoric acid solution, H3Po4) at a high temperature (e.g., about 160° C. to about 180° C.) stored in a process tank, so that the silicon nitride film of each wafer is etched. Thus, the silicon nitride film on the surface of the wafer is formed into a desired pattern.
The process tank is of a rectangular parallelepiped shape, and has four sidewalls and a bottom plate. Heaters are provided on the respective sidewalls and the bottom plate. Thus, the chemical liquid stored in the process tank can be heated before wafers are immersed thereinto and while the wafer is being immersed therein.
In addition, the substrate processing apparatus is provided with a wafer board including a holding rod for holding a plurality of wafers in a standing state (in a vertical state), and a back plate connected to the holding rod and extending vertically. Wafers are held by the holding rod of the wafer board, and are immersed into the chemical liquid that is heated in the boiling state.